Influence of chain length of diol on the swelling behavior of citric acid based pH sensitive polymeric hydrogels: A green approach

Synthesis of pH‐sensitive hydrogels of citric acid with varying diol units viz., 1,2 Ethane diol, 1,4 butane diol, and 1,6 hexane diol along with methacrylic acid towards the solventless green approach. The formations of the hydrogels were identified using FTIR spectroscopy. Thermal characterization (thermo gravimetric analysis, differential thermal analysis (DTA), and differential scanning calorimetry) and morphology of the synthesized hydrogels have been investigated. Swelling studies of hydrogels in various pH ranging from 4.0 to 10.0 have been investigated. The results of the swelling studies implied that percentage of swelling comparatively higher at neutral pH (7.4) than at acidic and alkaline pH. The inverse relationship was noticed, where ascending the diol units of hydrogel in swelling equilibrium. The hydrogels with the increasing chain length show a noticeable pH sensitivity and which could be considered as smart hydrogel. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41403.     

Curing copolymerization kinetics of styrene with maleated castor oil glycerides obtained from biodiesel‐derived crude glycerol

Kinetics of curing of maleated castor oil glycerides with styrene was studied by differential scanning calorimetry and rheology. The resin was synthesized from biodiesel‐derived crude glycerol. Curing rates were fitted to several empirical models (autocatalytic model, Kamal's model and a model with vitrification). The three models showed a good fitting with experimental data at conversions lower than 0.55 for temperatures ranging from 30 to 50°C. However, the model that includes vitrification showed a better fitting in the entire range of conversions and the same temperatures. At higher temperatures (50–60°C), some deviations were observed for the three models at low and high conversions. Gel times were obtained from rheological studies and the apparent activation energies were calculated thereof. Gel times were 300–2700 s. The values of apparent activation energy obtained for this castor oil‐based copolymer (47.2–52.3 kJ/mol) were within range of commercial unsaturated polyester resins. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41344.     

The effect of radiopacifiers agents on pH,calcium release,radiopacity, and antimicrobial properties of different calcium hydroxide dressings

The aim of this study was to evaluate the antimicrobial activity, pH level, calcium ion release, and radiopacity of calcium hydroxide pastes associated with three radiopacifying agents (iodoform, zinc oxide, and barium sulfate). For the pH and calcium release tests, 45 acrylic teeth were utilized and immersed in ultrapure water. After 24 h, 72 h, and 7 days the solution was analyzed by using a pH meter and an atomic absorption spectrophotometer. Polyethylene tubes filled with the pastes were used to perform the radiopacity test. For the antimicrobial test, 25 dentin specimens were infected intraorally in order to induce the biofilm colonization and treated with the pastes for 7 days. The Live/Dead technique and a confocal microscope were used to obtain the ratio of live cells. Parametric and nonparametric statistical tests were performed to show differences among the groups (P < 0.05). The pH analysis at 7 days showed significant differences (P < 0.05) among the groups. No differences among the pastes were found in the calcium release test on the 7th day (P > 0.05). The calcium hydroxide/iodoform samples had the highest radiopacity and antimicrobial activity against the biofilm‐infected dentin in comparison to the other pastes (P < 0.05). Calcium hydroxide mixed with 17% iodoform and 35% propylene glycol into a paste had the highest pH, calcium ion release, radiopacity, and the greatest antimicrobial action versus similar samples mixed with BaSO4 or ZnO. Microsc. Res. Tech. 78:620–625, 2015. © 2015 Wiley Periodicals, Inc.     

Urban Real Estate in Ghana: A Study of Housing-related Remittances from Australia

A combination of rapid population growth and low incomes results in housing shortages in Ghana. Migration to Europe, America and Scandinavia has provided a way for some Ghanaians to escape this housing problem, as they take advantage of salaries there in order to save and build houses much quicker back home. This study of Ghanaian migrants in Sydney shows that by keeping at two or more jobs and saving about 33 per cent of their incomes, they are able to build houses worth US$100 000 in Ghana within 3–6 years. How these Ghanaians acquire land, how they build and their experiences after completing their houses provide clues on how to improve housing policy in Ghana.     

Fissure formation and subsurface subsidence in a coalbed fire

Coalbed fires are uncontrolled subsurface fires that occur around the world. These fires are believed to be significant contributors to annual CO₂ emissions. Although many of these fires have been burning for decades, researchers have only recently begun to investigate physical mechanisms that control fire behavior. One aspect of fire behavior that is poorly characterized is the relationship between subsurface combustion and surface fissures. At the surface above many fires, long, wide fissures are observed. At a coalbed fire near Durango, Colorado, these fissures form systematic orthogonal patterns that align with regional joints in the Upper Cretaceous Fruitland Formation. Understanding the mechanisms that form these fissures is important, as the fissures are believed to play vital roles in sustaining the combustion in the subsurface. In some of the coalbed fire simulation models available today, these fissures are treated as fixed boundary conditions. We argue, using data collected, field observations and simulation result, that there exists a relationship between the location and magnitude of subsidence caused by the fire and the opening of fissures. The results presented suggest that fissures are believed to open when subsurface subsidence gives rise to tensile stresses around pre-existing joints.     

High Thermal Conductivity Polymer Composites Fabrication through Conventional and 3D Printing Processes: State-of-the-Art and Future Trends

The lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials.     

Perfluorinated acids in Arctic snow: new evidence for atmospheric formation

Perfluorinated acids (PFAs) are ubiquitously found in water and biota, including remote regions such as the High Arctic. Under environmental conditions, PFAs exist mainly as anions and are not expected to be subject to long-range atmospheric transport in the gas phase. Fluorinated telomer alcohols (FTOHs) are volatile and can be atmospherically oxidized to form perfluorocarboxylic acids. Analogously, fluorosulfamido alcohols can be oxidized to form perfluorooctane sulfonate (PFOS). High Arctic ice caps experience contamination solely from atmospheric sources. By examining concentrations of PFAs in ice cap samples, it is possible to determine atmospheric fluxes to the Arctic. Ice samples were collected from high Arctic ice caps in the spring of 2005 and 2006. Samples were concentrated using solid-phase extraction and analyzed by LC-MS-MS. PFAs were observed in all samples, dating from 1996 to 2005. Concentrations were in the low-mid pg L(-1) range and exhibited seasonality, with maximum concentrations in the spring-summer. The presence of perfluorodecanoic acid (PFDA) and perfluoroundecanoic acid (PFUnA) on the ice cap was indicative of atmospheric oxidation as a source. Ratios of PFAs to sodium concentrations were highly variable, signifying PFA concentrations on the ice cap were unrelated to marine chemistry. Fluxes of the PFAs were estimated to the area north of 65 degrees N for the 2005 season, which ranged from 114 to 587 kg year(-1) for perfluorooctanoic acid (PFOA), 73 to 860 kg year(-1) for perfluorononanoic acid (PFNA), 16 to 84 kg year(-1) for PFDA, 26 to 62 kg year(-1) for PFUnA, and 18 to 48 kg year(-1) for PFOS. The PFOA and PFNA fluxes agreed with FTOH modeling estimations. A decrease in PFOS concentrations through time was observed, suggesting a fast response to changes in production. These data suggest that atmospheric oxidation of volatile precursors is a primary source of PFAs to the Arctic.     

Composition and properties of milk and butter from cows fed fish oil

A control diet and a fish oil diet were fed to 12 multiparous Holstein cows to determine how the incorporation of Menhaden fish oil in the diet would influence the fatty acid composition, especially the conjugated linoleic acid and transvaccenic acid, contents of milk and butter. The control diet consisted of a 50:50 ratio of forage to concentrate, and the fish oil diet consisted of the control diet with 2% (on a dry matter basis) added fish oil. Milk from cows fed the control diet contained higher average concentrations of milk fat (3.37%) compared with milk from cows fed the fish oil diet (2.29%). Milk from cows fed fish oil contained higher concentrations of conjugated linoleic acid, transvaccenic acid, and total unsaturated fatty acids (0.68 and 2.51; 1.42 and 6.28; and 30.47 and 41.71 g/100 g of fat, respectively). Butter made from the fish oil diet milk also had higher concentrations of conjugated linoleic acid, transvaccenic acid, and unsaturated fatty acids. Penetrometer readings indicated fish oil diet butters were softer at 4 and 20 degrees C than the control diet butters. Acid degree values were similar in the fish oil butters compared with the control butters. No significant difference was found in the flavor characteristics of milk and butter from cows fed the control and fish oil diets. Production of milk and butter with increased amounts of conjugated linoleic acid, transvaccenic acid, and other beneficial fatty acids may have a desirable impact on the health of consumers and lead to increased sales.     

Effects of ketones, acetate, butyrate, and glucose on bovine lymphocyte proliferation

Blood leukocytes from age-matched heifers were used to determine effects of ketones, acetate, butyrate, and glucose on in vitro lymphocyte proliferation. Lymphocytes stimulated with concanavalin A, phytohemagglutinin-P, or pokeweed mitogen were cultured in the presence or absence of beta-hydroxybutyrate, acetoacetate, acetone, acetate, butyrate, and glucose. Only supraphysiological levels of beta-hydroxybutyrate inhibited proliferation in cultures of mitogen-stimulated lymphocytes, whereas mixtures of beta-hydroxybutyrate and acetoacetate at levels seen in severe ketosis stimulated concanavalin A and phytohemagglutinin-P-driven proliferation. Because acetoacetate was a lithium salt, lithium chloride served as a negative control. Results suggest the enhanced proliferation by cultures containing lithium acetoacetate was due to lithium, not acetoacetate. Butyrate (at concentrations greater than seen in bovine plasma) and acetate at normal levels inhibited proliferation. Concanavalin A- and pokeweed-mitogen-driven proliferation was greater in cultures containing lower glucose levels, but acetate added to cultures containing low glucose inhibited concanavalin A-stimulated proliferation. Proliferation by pokeweed mitogen-stimulated cultures containing acetate, beta-hydroxybutyrate, and acetoacetate was suppressed at the lower concentrations of glucose tested. In conclusion, ketones, butyrate, and glucose at concentrations occurring in vivo had minimal effects on bovine lymphocyte proliferation in vitro. Levels of acetate associated with ketosis suppressed lymphocyte function and may alter immune responsiveness in vivo.     

Transrectal ultrasound applicator for prostate heating monitored using MRI thermometry

PURPOSE: For potential localized hyperthermia treatment of tumors within the prostate, an ultrasound applicator consisting entirely of nonmagnetic materials for use with magnetic resonance imaging (MRI) has been developed and tested on muscle tissue ex vivo and in vivo. METHODS AND MATERIALS: A partial-cylindrical intracavitary transducer consisting of 16 elements in a 4 x 4 pattern was constructed. It produced a radially propagating acoustic pressure field. Each element of this array (1.5 x 0.75 cm), operating at 1.5 MHz, could be separately powered to produce a desired energy deposition pattern within a target volume. Spatial and temporal temperature elevations were determined using the temperature-dependent proton resonant frequency (PRF) shift and phase subtraction of MR images acquired during ultrasonic heating. Four rabbits were exposed to the ultrasound to raise the local tissue temperature to 45 degrees C for 25 minutes. Six experiments compared thermocouple temperature results to PRF shift temperature results. RESULTS: The tests showed that the multi-element ultrasound applicator was MRI-compatible and allowed imaging during sonication. The induced temperature distribution could be controlled by monitoring the RF power to each transducer element. Therapeutic temperature elevations were easily achieved in vivo at power levels that were about 16% of the maximum system power. From the six thermocouple experiments, comparison between the thermocouple temperature and the PRF temperature yielded an average error of 0.34+/-0.36 degrees C. CONCLUSIONS: The MRI-compatible intracavitary applicator and driving system was able to control the ultrasound field and temperature pattern in vivo. MRI thermometry using the PRF shift can provide adequate temperature accuracy and stability for controlling the temperature distribution.